(1) Field of the Invention
The present invention relates to novel platinum complexes, processes for the synthesis of the same, and pharmaceutical compositions for the treatment of malignant tumors which contains the same as the active ingredient.
(2) Description of the Related Art
The clinical application of cis-diamminedichloroplatinum (II) (hereinafter referred to as "CDDP") has recently brought marked progress in the chemotherapy of malignant tumors. Namely, CDDP shows a high antitumor activity towards cancers of sexual organs such as ovary and testis. However, in clinical use, CDDP causes serious problems due to severe adverse effects including toxic effects on the kidney and the bone marrow. In this connection, renal toxicity is generally considered to be a dose-limiting factor (DLF) in the clinical use of CDDP, and thus, a number of studies have been carried out to reduce the renal toxicity or to seek other platinum complexes with a reduced toxicity. Platinum(II) cis-diamine-1,1-cyclobutanedicarboxylate (hereinafter referred to as "CBDCA") and platinum(II) cis-diamine-O,O'-glycolate (see Japanese Unexamined Patent Publication No. 56-154,493, etc.) have been developed as a result of such studies and are regarded as the second generation of platinum antitumor agents.
These compounds do exhibit a reduced renal toxicity, compared with CDDP, but their anti-tumor activity is also reduced compared with that of CDDP. Therefore, platinum complexes having a high antitumor activity and a low toxicity must be developed.